NEW YORK, Dec 16 ― The number of Americans who identify as non-religious is soaring in the profoundly Christian United States, according to a Pew Research Center study published Tuesday.

Some 29 per cent of American adults are now religiously unaffiliated ― up from 16 per cent 14 years ago ― the survey found.

America is home to a powerful, socially conservative Christian right-wing political faction and Christianity remains the overwhelmingly dominant religion in the country.

But the religion is declining markedly, the Pew results showed.

Seventy-eight per cent of US adults identified as Christian in 2007. Now, some 63 per cent do, according to the research.

In 2007, Pew began tracking religious "nones” ― people who describe themselves as atheist, agnostic or "nothing in particular.”

Then, Christians outnumbered nones by almost five-to-one. Today it is closer to two-to-one, the researchers said.

Pew's researchers did not give reasons for the trend, but it is in line with the wider decline in Christianity across the West.

In 2019, the centre said the growth of religious nones in America was particularly evident among younger people.

Pew's latest survey found that the secular shift was concentrated amongst Protestant communities, with the Catholic share of the population holding relatively steady in recent years.

Some 60 per cent of Protestants described themselves as born-again or evangelical Christian, Pew said.

White evangelical Christians are among former president Donald Trump's most ardent supporters, with 84 percent of the group voting for him in last year's election, Pew said previously.

Researchers quizzed almost 4,000 respondents between May and August this year for the survey released Tuesday. ― ETX Studio